The present invention relates to a backlight unit using, for example, light emitting diodes (LED's) as light source for illuminating a liquid crystal panel and an image display using the same and more particularly to a backlight unit including light guide plate for guiding light from the light emitting diodes to liquid crystal panel and an image display using the same.
In order to conform to regulations of energy saving in recent years, even a backlight unit used in an image display using liquid crystal panel is required to reduce power consumption. Accordingly, area control (also named area dimming or local dimming) in which a backlight unit is divided into plural blocks and intensity of light emitted from each block is controlled in accordance with brightness of image corresponding to each block is put to practical use.
On the other hand, the edge-light type backlight unit known as one system of backlight unit converts point light from light emitting diodes into surface light by means of plate-like light guide plate made of transparent resin to irradiate liquid crystal panel with surface light, so that it is advantageous to make image display thinner (reduction in depth).
JP-A-2007-293339 (US2007/0247871) and JP-A-2010-021131 (US2009/0303410), for example, are known as prior arts of performing area dimming in the edge-light type backlight unit. These prior arts disclose that plural blocks each including light emitting diodes and light guide plate combined in a set are arranged and light intensity of light emitting diodes corresponding to each block is controlled individually to make light dimming.